Copolymers of diallyl barbituric acids and sulfur dioxide



United States Patent 3,134,756 COPOLYIVIERS 0F DIALLYL BARBITURIC ACIDSAND SULFUR DIOXiDE John 'R. Mattson, Maplewood, Minn, assignor toMinnesota Mining and Manufacturing Company, St. Paul, Minn, acorporation of Delaware No Drawing. Filed Dec. 5, 1960, Ser. No. 73,480

3 Claims. (Cl. 26079.3)

This invention relates to certain new and useful linear copolymersderived from sulfur dioxide and diallylbarbituric acids. These newlinear copolymers can be termed poly-Spiro[3'-sulfonylmethyl-cyclohexyl-l,5-(barbiturate)] and are representedgenerically by the formula:

OH SOz A-M n where R is selected from the group consisting of hydrogenand lower alkyl, A is selected from the group consisting ofoxygen andsulfur, M is selected from the group consisting of alkali metals andammonium, n is a positive whole number ranging from aboutS to 300.

As used in this application, the term lower has reference to less than 7carbon atoms, and the term alkali .metals has reference to those metalsof group I-A of the periodictable of the elements, such as lithium,potassium, sodium, etc.

Preferred compounds of this invention are those of Formulas 1 and '2wherein R and R are hydrogen, A is selected from the group consisting ofoxygen and sulfur, M is sodium.

The compounds of this invention are readily prepared by contacting theappropriate diallylbarbituric acid compound with sulfur dioxide. Theoverall reaction can be summarized as follows:

. 0 If, OHFCHOH, ii-N radical 0 C=A so, initiator OHFOHOH, G-N (4) fiOH2SO2 0:0 (3:0 Ii -N /NRz' I i A In Any suitable radical initiatorknown to the art can be used to initiate the reaction. Of course,variations in the degree of radical formation produced by a giveninitiator, or a combination of initiators, will be observed with anygiven set of reactants. As those skilled in the art will readilyappreciate, radical initiators whichare degraded or otherwiseinactivated by sulfur dioxide obviously will not produce the desiredreaction. Suitable radical initiators include, for example, suchmaterials as lauroylperoxide, benzoylperoxide, azobisisobutyronitrile,ditertiarylbutylperoxide, dicumylperoxide, actinic radiation such asultraviolet light and the like.

Concerning quantity of the reactants employed, I prefer to use at leasta percent molar excess of S0 More preferably, I prefer to use at least a300 percent molar excess of S0,, with respect to the diallylbarbituricacid compound of Formula 3.

The amount of chemical radical initiator employed for a given reactioncan in general vary between wide limits. Usually one will employ atleast about 0.001 percent to 1 percent of radical initiator based on thecombined weight of reactants. Commonly, not more than about 3 percent ofradical initiatorwill be employed based on combined weight of reactants.The optimum amount of radical initiator to be employed in any givenreaction will of course vary from reaction to reaction, and it is notpossible to give the exact amount for every given combination ofreaction conditions and reactants. However, as those of ordinary skillin the art will appreciate, one will use an amount of radical initiatorwhich is sufiicient to cause a reaction to proceed. When ultravioletlight is used as the radical initiator, one will employ an amount ofillumination which will induce sulfur dioxide to react with compounds ofFormula 3.

In general, I conduct the reaction at about 50 to 100 C., the optimumreaction temperature for any specific reaction is that which willproduce the greatest extent of reaction between the compounds. Reactiontimes are generally under 24 hours.

The extent of the reaction after a given reaction period can bedetermined by distilling off the excess S and extracting the solidresidue with hot alcohol (i.e., ethano1). The alcoholic solution isevaporated to dryness and the amount of residue which consists ofunreacted compound of Formula 3 is determined gravimetrically.

The molecular weight is controlled by the use of chain transfer agentssuch as mercaptans and tetrahalomethanes (i.e., ethyl, butyl, actylmercaptans and trichlorobromo, or dichlorodibromomethane). Varyingproportions of chain transfer agent to 80;; gives products having arange of n from about 5 to 300.

The starting materials of Formula 3 can be prepared by any conventionalmeans known to the art. Diallylbarbituric acid itself is commerciallyavailable and can be used to prepare the N-lower alkyl substitutedderivatives by conventional alkylation procedures; see for example theprocedures. described in: Chemical Abstracts, 28, 2370 (1934), Chem.Abstract 27,5083 (1933.), Chem. Abstract 42, 573 (1948), Chem. Abstract44, 6525 (1950), Chem. Abstract 46, 3154 (1952).

N-alkyl or N,N-dialkylderivatives of 5,5-diallyl barbituric acid can bemade from the corresponding urea or thiourea derivatives anddiallylmalonic ester.

I prefer to use S0 which is substantially free from impurities, but thepurity of the S0 is, in'general, not critical in producing products ofthe invention.

The metal and ammonium salts of Formula 2 are readily prepared from theappropriate free acidic compounds of Formula 1 by merely adding analcoholic solution of an inorganic base containing the desired cation toa solution of the compound of Formula -1 in dimethylformamide.Similarly, to prepare amine salts, one simply adds a dimethylformamidesolution of the appropriate compound of Formula 1. to an alcoholicsolution of the desired amine. The solvent is then removed bydistillation at low pressure.

Products of this invention prepared by the routes described above'arecomprised of optically active isomers, e.g., due to asymmetry about thecommon spiro carbon atom. The levoforms are believed to have the mostbiological activity. V

Higher molecular weight polymers of Formula 1 (i.e., those of Formula 1when n is greater than form an interesting and useful class of ionexchange resins when Formula 1, the compounds appear to be convulsants.The

salts tend to have greater Water solubility than the polymers ofFormula 1. High molecular weight compounds have pharmacological utilityespecially tranquilizing activity.

The invention is further illustrated by refernece to the followingexamples:

EXAMPLE I Poly-Spiro [3-Sulj0nylmethyl-Cyciohexyl-l ,5- (BarbituricAcid) Diallylbarbituric acid 5 g. (0.024 mole), azobisisobutyronitrile0.25 g. and 3.22 ml. of liquid S0 is charged to a 25 ml. Pyrex ampoulewhile flushing with nitrogen. The ampoule is cooled in liquid air,evacuated and sealed off. After heating with gentle agitation at C. for22 hours the ampoule is cooled in Dry Ice and opened. The excess S0 isallowed to evaporate leaving about 6.2 grams of White solid productmelting over 250 C. with decomposition. 1

The product is dissolved in hot dimethylformamide and poured into alarge excess of absolute ethanol. This process is repeated three times.The purified material is pulverized and dried at 120 C.

Calculated for [C10H12N205S] i C, H, 9.9% N, 11.3% S, where n is about100. Found: 42.0% C, 5.2% H, 10.7% N, 11.3% S. Inherent viscosity 0.65in dimethylformamide.

EXAMPLE II for 18 hours, the ampoule is aagin cooled in Dry Ice and Rand preferably also R are hydrogen. The polymers 7 also serve as usefulvehicles for. fluorescent dyes.

Especially when A is sulfur in Formulas 1 or 2, the

polymers are valuable tarnishproofing agents and can be incorporatedinto silver polishing compositions.

When lower molecular weight molecular weight polymers in Formula 1 (suchas those of Formula 1 where n V open. The excess sulfur dioxide isallowed to evaporate. The reaction mixture is removed from the ampoule,dis-' solved in hot dimethyl formamide and poured into a large excess ofethanol. This process is repeated 3 times and 5 g. of purified materialis obtained. According to viscosity measurements this product has avalue of 11 equal to about 10. V EXAMPLE III Salts ofPoly-Spiro[3'-Sulf0nylmethyl-Cyclohexyl- 1',5-(Barbituric Acid)] To asolution of 0.1 equivalent of the free acid in ml. of dimethylformamideis added a solution of 0.1 mole of sodium hydroxide in 30 ml. ofethanol. The precipitate which consists of sodiumpoly-spiro[3'-sulfonylmethyl-cyclohexyl-l,5-(barbituric acid)] is driedunder vacuum at about 50 C. for several hours. The same procedure isfollowed using corresponding stoichionietric.

equivalents of potassium hydroxide, and ammoinum hydroxide or a simplesubstituted ammonium hydroxide to prepare respectively, the K andammonium salts of polyspiro[3' sulfonylmethyl cyclohexyl 1,5 (barbituricacid)].

The following examples presented in tabular form as Table I show thepreparation of additional'compounds of Formula 1. A ten mole percentexcess of sulfur dioxide over the amount of compounds of Formula 3 isemployed in each instance. The amount of radical initiator employed isabout 1 percent based on combined weight of reactants. Reaction time isabout 24 hours in each instance. In all examples n is greater than 100,-

TABLE I Substituents of Compounds of Formula 3 Example Catalyst ProductA. R1 R2 IV S H H Benxoyl- F CH2SO3 peroxide.

I A? O HNYNH S n r V O CH; H Benzoyl- CHzSO2-- peroxide.

0 (|3 0 EN N CH3 C O n VI S n-G3H1 H Benzoyl- CH2SOz peroxide.

0 FA? 0 EN N-CaH O S n f V11- 0 nCoHia 11-0511, Azobisiso- CH2SO2butyronitrile.

O (1 (I3 0 CaHrs-N N CoHia The claims are: 1. A linear copolymercomposed substantially of repeating units of the formula:

where n is an integer from about 5 to 300.

3. A metal salt of a linear copolymer according to claim 2, said metalsalt being a copolymer of the formula wherein R is selected from thegroup consisting of hydrogen and lower alkyl, A is selected from thegroup consist- 7 ing of oxygen and sulfur, M is selected from the groupconsisting of alkali metals and ammonium and n is a positive wholenumber from about 5 to 300.

References Cited in the file of this patent UNITED STATES PATENTS HussyApr. 2, 1918 OTHER REFERENCES Butler et 21.: Journal of AmericanChemical Society volume 79 (1957), pages 31283131.

Chemical and Engineering News, volume 36, April 21, 1958, page 44.

1. A LINEAR COPOLYMER COMPOSED SUBSTANTIALLY OF REPEATING UNITS OF THEFORMULA: